CH3OC(O)NCO

CH₃OC(=O)N=C=O

Nitrogen

Nuclear Quadrupole Coupling Constants

in Methoxycarbonyl isocyanate

¹⁴N nqcc's in methoxycarbonyl isocyanate were determined by Watanabe, et al. [1]. Calculation was made here of the ¹⁴N nqcc tensor on r_opt molecular structures derived by B3LYP and MP2 optimizations, each with 6-311+G(3df, 3pd) and cc-pVTZ bases (assuming C_s symmetry). These are compared with the experimental nqcc's in Tables 1 and 2. Structure parameters are given in Z-matrix format in Table 3. Rotational constants are compared in Table 4.

In Tables 1 and 2, subscripts a,b,c refer to the principal axes of the inertia tensor; x,y,z to the principal axes of the nqcc tensor. ETA = (X_xx - X_yy)/X_zz.

RMS is the root mean square difference between calculated and experimental diagonal nqcc's (percentage of the average of the magnitudes of the experimental nqcc's). RSD are the calibration residual standard deviation of the B3PW91/6-311+G(df,pd) model for calculation of the efg's/nqcc's.


Table 1. ¹⁴N nqcc's in Methoxycarbonyl isocyanate (MHz). Calculation was made on B3LYP/6-311+G(3df,3pd) and MP2/6-311+G(3df,3pd) optimized molecular structures.

		B3LYP		MP2		Expt [1]

X_aa		2.938		2.915		3.0065(11)
X_bb	-	1.639	-	1.583	-	1.5949(16)
X_cc	-	1.299	-	1.332	-	1.4116(16)
X_ab		0.400		0.302

RMS		0.080 (4.0 %)		0.070 (3.5 %)
RSD		0.030 (1.3 %)		0.030 (1.3 %)

X_xx	-	1.674	-	1.604
X_yy	-	1.299	-	1.332
X_cc		2.973		2.936
ETA	-	0.126	-	0.0926


Table 2. ¹⁴N nqcc's in Methoxycarbonyl isocyanate (MHz). Calculation was made on B3LYP/cc-pVTZ and MP2/cc-pVTZ optimized molecular structures.

		B3LYP		MP2		Expt [1]

X_aa		2.930		2.902		3.0065(11)
X_bb	-	1.632	-	1.567	-	1.5949(16)
X_cc	-	1.298	-	1.335	-	1.4116(16)
X_ab		0.407		0.295

RMS		0.082 (4.1 %)		0.076 (3.8 %)
RSD		0.030 (1.3 %)		0.030 (1.3 %)

X_xx	-	1.668	-	1.586
X_yy	-	1.298	-	1.335
X_cc		2.966		2.922
ETA	-	0.125	-	0.0858


Table 3. Methoxycarbonyl isocyanate. B3LYP and MP2 optimized structure parameters. (Å and degrees).

		C O,1,B1 O,1,B2,2,A1 C,3,B3,1,A2,2,D1,0 H,4,B4,3,A3,1,D2,0 H,4,B5,3,A4,1,D3,0 H,4,B6,3,A5,1,D4,0 N,1,B7,2,A6,3,D5,0 C,8,B8,1,A7,2,D6,0 O,9,B9,8,A8,1,D7,0

	B3LYP/6-311+G(3df,3pd)	MP2/6-311+G(3df,3pd)

	B1=1.20074617 B2=1.33136798 B3=1.43853165 B4=1.08443229 B5=1.08756812 B6=1.08756812 B7=1.39985645 B8=1.21352279 B9=1.1570087 A1=125.83891612 A2=115.37320554 A3=105.3010063 A4=110.30504932 A5=110.30504932 A6=125.52634517 A7=130.38307006 A8=173.40247177 D1=0. D2=180. D3=-60.49409536 D4=60.49409536 D5=180. D6=0. D7=180.	B1=1.20483808 B2=1.32984078 B3=1.43510142 B4=1.08281736 B5=1.08615369 B6=1.08615369 B7=1.40111711 B8=1.22317328 B9=1.16453118 A1=125.92119334 A2=113.66143936 A3=105.18929025 A4=110.14314415 A5=110.14314415 A6=125.96335352 A7=127.29781355 A8=172.6860178 D1=0. D2=180. D3=-60.42725385 D4=60.42725385 D5=180. D6=0. D7=180.

	B3LYP/cc-pVTZ	MP2/cc-pVTZ

	B1=1.2015855 B2=1.33320587 B3=1.43920613 B4=1.08497014 B5=1.08813488 B6=1.08813488 B7=1.40088299 B8=1.21347221 B9=1.15865206 A1=125.93973902 A2=115.11433537 A3=105.29295321 A4=110.38122347 A5=110.38122347 A6=125.61412059 A7=130.46024813 A8=173.35515661 D1=0. D2=180. D3=-60.47812035 D4=60.47812035 D5=180. D6=0. D7=180.	B1=1.2060757 B2=1.33310738 B3=1.4365205 B4=1.08292259 B5=1.0861393 B6=1.0861393 B7=1.40262854 B8=1.22423117 B9=1.16718231 A1=125.97056539 A2=113.22345475 A3=105.25629338 A4=110.30516028 A5=110.30516028 A6=126.08227138 A7=126.7170313 A8=172.52027378 D1=0. D2=180. D3=-60.43839514 D4=60.43839514 D5=180. D6=0. D7=180.


Table 4. Methoxycarbonyl isocyanate. Rotational Constants (MHz).

6-311+G(3df,3pd)		B3LYP/	MP2/	Expt [1]

	A	11087.	11049.	11041.67903(37)
	B	1392.	1391.	1417.838077(66)
	C	1247.	1245.	1266.547230(87)

cc-pVTZ		B3LYP/	MP2/

	A	11052.	11014.
	B	1409.	1411.
	C	1260.	1260.

[1] S.Watanabe, Y.Kawashima, and N.Kuze, Abstract ML06, 73rd ISMS, Champaign-Urbana, Illinois, 2018.

HNCO

CH₃NCO

CH₃CH₂NCO

t-(CH₃)₃CNCO

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Molecules/Nitrogen

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Last Modified 18 Nov 2018